Spatial distribution of soil δ13C in the central Brazilian savanna

Stable carbon isotope ratios (δ13C) of soil record information regarding C3 and C4 plants at the landscape scale that can be used to document vegetation distribution patterns. The Central Brazilian savanna (locally called the Cerrado) has a substantial potential to develop studies of patterns of dynamics and distribution of soil δ13C, due to its environmental diversity. The purpose of this work was to develop a spatial model of soil δ13C (soil δ13C isoscape) to the Cerrado, based on multiple linear regression analysis, and compare the results with the existing model to obtain greater detail of the soil δ13C distribution. The model used 219 soil samples (0–20 cm depth) and a set of climatic, pedological, topographic, and vegetation correlations. The soil δ13C isoscape model presentedamplitude between - 29‰ and -13‰, with the highest estimated values in the southern and the lowest values inthe northern of the Cerrado. Results indicate that soil δ13C, by reflecting the relative contribution of C3 and C4 species to plant community productivity, served as a proxy indicator of the vegetation history at the landscape scale for the Central Brazilian savanna. Despite the large sampling effort, there are still regions with some gaps that the model could not estimate. However, the soil δ13C isoscape model filled most the existing gaps and provided greater detail of some unique local aspects of the Cerrado.

土壤稳定碳同位素比值（δ¹³C）可记录景观尺度下C3、C4植物的相关信息，能够用于刻画植被分布格局。巴西中部稀树草原（当地称塞拉多（Cerrado））环境多样，在开展土壤δ¹³C动态与分布格局研究方面具备显著潜力。本研究基于多元线性回归分析，构建了适用于塞拉多地区的土壤δ¹³C同位素景观图（soil δ¹³C isoscape）模型，并将该模型结果与现有模型进行对比，以获取更精细的土壤δ¹³C分布细节。该模型共纳入219份0~20 cm深度的土壤样品，以及一系列气候、土壤学、地形与植被相关关联因子。该土壤δ¹³C同位素景观图模型的取值区间为-29‰至-13‰，估算得到的最高值分布于塞拉多南部，最低值则集中在北部区域。研究结果表明，土壤δ¹³C可通过反映C3与C4植物对植物群落生产力的相对贡献，作为巴西中部稀树草原景观尺度下植被历史的替代指示指标。尽管本次研究开展了大量采样工作，但仍存在部分区域无法通过模型完成估算。不过，该土壤δ¹³C同位素景观图模型填补了绝大多数现存数据空白，并为塞拉多部分独特的局域特征提供了更精细的分布细节。